Introduction to Tableau and Data Visualization
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# Colour for Time-Data Analysis

We will now use colour to evaluate which category has been most profitable over time. This will be done in three steps.

1. Create a parameter based on the profitability field.
2. Reference line that adjusts based on the parameter value
3. Colour any values below the reference line as red; and values above as green.

## Step 1

Create a new parameter named threshold

By default it is float data type. As we are dealing with such a large range of numbers, decimals wouldn't be suitable. It would make more sense to use integer values. This parameter will range from $1 to$10,000.

Varying this threshold parameter will have no impact since it's not connected to anything. We must somehow connect it to the reference lines that we're about to create.

Step 2

Since we will have a reference line for each vertical axis, click on one of the vertical axes and add reference line.

Each reference line will span its own pane. To connect each line to the parameter, specify that each line will reference the **threshold **value. The threshold value is also assigned to the label of each line.

And it works out!

## Step 3

The last step is to assign a categorical colour scheme. If values fall above the reference line, then they will be coloured green, otherwise, else, the values will be coloured red.

This can be done with a simple calculated field. If the profit sum is larger than the threshold value, categorize it as TRUE, otherwise FALSE.

That's all. By dragging this field to colour, the visualization's colour scheme is now dictated by this logic. Anything that falls below the threshold is blue; anything that falls above is orange.

To change this colour scheme, feel free to double click on the legend and select new colours.

Overall, the colour scheme is very effective in showing that technology is much more profitable over time.

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